Cryptosporidiosis in children during a massive waterborne outbreak in Milwaukee, Wisconsin: clinical, laboratory and epidemiologic findings

During the spring of 1993 an estimated 403000 residents of the greater Milwaukee, Wisconsin area experienced gastrointestinal illness due to infection with the parasite Cryptosporidium parvum following contamination of the city's water supply. To define the clinical, laboratory and epidemiologic features of outbreak-associated cryptosporidiosis in children, medical and laboratory records for all children submitting stool samples to the microbiology laboratory of the Children's Hospital of Wisconsin between 7 April and 13 May 1993 were reviewed retrospectively. Interviews with parents were also conducted to obtain additional clinical history. Cryptosporidium, as the sole pathogen, was identified in stools from 49 (23%) of the 209 children enrolled in the study. Children with laboratory-confirmed cryptosporidiosis were more likely to live in areas of Milwaukee supplied with contaminated water (RR=1·92, CI=1·19–3·09), to be tested later in their illness (P